Juvenile Onset Huntington Disease (JHD) is a form of Huntington disease (HD) that affects children and teenagers. Huntington
disease is a hereditary neurodegenerative disorder that is characterized by progressively
worsening motor, cognitive, behavioral, and psychiatric symptoms. JHD is caused by
a mutation of the Huntington gene called a “CAG repeat expansion”. The mutation results
in gradual neuronal degeneration in the basal ganglia of the brain, which is responsible
for coordination of movements, thoughts, and emotions. As JHD progresses, other regions
of the brain undergo neuronal degeneration with diffuse and severe brain atrophy that
is comparable to late stage Alzheimer disease.

Presentation of JHD includes changes in personality, coordination, behavior, speech
or ability to learn. Physical changes include rigidity, leg stiffness, clumsiness,
slowness of movement, tremors or myoclonus. In comparison with adult HD, seizures
and rigidity are common, and chorea is uncommon.

DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND ICD-9-CM CODING

Diagnostic testing: The diagnosis of JHD is made by clinical history documenting changes in motor, behavioral
and cognitive function, family history of HD, abnormal neurologic exam findings, abnormal
neuropsychological test results, and HD gene test with abnormal results. Brain imaging
is optional, but if performed, may show atrophy of the caudate nucleus or (in very
young children) the cerebellum, or diffuse brain atrophy.

ICD-9: 333.4

ONSET AND PROGRESSION

JHD usually has a more rapid progression rate than adult onset HD; the earlier the
onset, the faster JHD progresses. Death often occurs within 10 years of JHD onset,
as opposed to 10-25 years in adult onset HD.

TREATMENT

There is no cure or treatment to stop, slow or reverse the progression of JHD. Medications
may be prescribed to manage symptoms. A child psychiatrist or behavior management
specialist may address behavior disorders. A speech language pathologist may evaluate
communication and swallowing problems. A nutritionist may be consulted to address
nutritional needs as the disease progresses. Assistive devices such as wheelchairs,
helmets, and communication boards may be used for safety, and to improve quality of
life.